I think for us it is 3-4 years old. We really had to enforce modesty with DD1 (now 8), because at five she was still stripping in front of other people. She just didn't care. DS is 4, I think he was maybe 3.5 or so when I started being uncomfortable naked around him. He will still be allowed to watch me bf our newbie (if she ever gets here!), and I also plan to allow all the kids in the room when I give birth. I just am not comfortable showering and dressing in front of the older two.
DH still occasionally showers with DS, usually when we are in a hurry. He also often walks around in his underwear. Neither bothers me, and if he's comfortable, that's fine. DD2 and DD3 both still shower with both of us. They will be 3 in Feb and 2 March. DD2 is special needs, so all the rules kind of fly out the window with her, so we'll see how long she showers with us. For now its great fun to throw them both in the tub when I shower, they are always a hoot.
Wife to Rich
, SAHM to Elliana
03/11, and Jeanette 12/12